U.S. Pat. No. 6,370,962 to Sullivan et al. discloses an apparatus for determining the tensile characteristics of a sample under dynamic conditions. The apparatus comprises a housing 16 containing a linear motor 20. The apparatus also comprises a leading jaw assembly 30 and a follower jaw assembly 32, which are mounted to a rail 26 for movement along the rail 26. Further provided are optical sensors 102, 104 and a force sensor 108. Prior to a test run, the jaw assemblies are coupled together, such as using magnets, see column 6, lines 19–20. A sample is mounted in the clamping jaws of the leading and follower jaw assemblies 30 and 32. The “sample S is entered into the test run without being under tensile load,” see column 7, lines 14–15. The follower jaw assembly 32 initially moves with the leading jaw assembly 30 until the former reaches catch assemblies 90, at which juncture it stops forward movement. The leading jaw assembly 30 continues movement causing a tensile load to be applied to the sample. It is noted that the linear motor 20 “must achieve the test velocity at the initiation of or prior to the test run,” see column 6, lines 34–36. The optical sensors 102, 104 as well as the force sensor 108 generate real-time data during the test run, see column 7, lines 3–6. That data is used to determine stress-strain characteristics of the sample S, see column 7, lines 11–14. It is believed that signals generated by the force sensor 108 are not used by a controller in this apparatus to control the position of either jaw assembly 30, 32 as a function of time.
U.S. Pat. No. 5,188,456 to Burke et al. also discloses an apparatus for determining the tensile characteristics of a sample under dynamic conditions. The apparatus comprises a first gripping jaw 18 coupled to a movable forcer 12. The forcer 12 and, hence, the gripping jaw 18, are moved via a linear stepper motor 10. A second fiber gripping jaw 24 is substantially fixed. It is also coupled to a load cell 32. Prior to a test run, the first jaw 18 is moved in a direction away from the second jaw 24 until an increase in load is sensed by the load cell 32, see column 6, lines 9–12. The first jaw 18 is then moved to a position, as determined by a controller, until the sample is elongated a predefined percentage, see column 6, lines 12–16. The controller then samples the load cell to determine the load on the sample, see column 6, lines 16–19. The '456 patent also contemplates the controller continuously sampling the load cell while the sample is being heated and control the movement of the first jaw 18 so that the load applied to the sample remains constant, see column 6, line 32 through column 7, line 33. It is believed that signals generated by the load cell are not used by the controller in this apparatus to control the position of the first gripping jaw 18 as a function of time.
It is further noted that MTS Systems Corporation produces a material testing system sold under the product name “810 Floor-Standing Systems,” see “http://www.mts.com/menusystem.asp?DataSource=0&NodeID=1011.” The apparatus comprises a fixed first workpiece gripping member and a movable second workpiece gripping member. The second member is caused to move away from the first member so as to apply a tensile load to a workpiece. Movement of the second member is effected via a servo-valve. The apparatus includes a conventional LVDT sensor for determining relative displacement between the first and second gripping members. It further includes a load sensor for generating signals indicative of the load applied by the workpiece to the first member. It is believed that signals generated by the load sensor are not used by a controller in this apparatus to control the position of the second workpiece gripping member as a function of time.